Supply device

ABSTRACT

The invention relates to a feeding device (F) for a mechanical weaving machine (T), comprising a winding element (W) which can be driven in a rotating manner, a stationary storage body (K), at least one stop element (S) which can be essentially axially and radially moved in relation to the storage body, between an unwinding position releasing thread yarn (Y) and a stop position which is applied to the foremost winding and which ends the weft insertion, in addition to a yarn clamp (C) which is arranged upstream from the stop element (S), which introduces the respective weft insertion, and which can be switched between a passive position an a clamping position. The inventive feeding device is characterised by a storage body (K) having a small diameter, and by a stop element (S) which can be exclusively moved axially to the stop position by the windings (YT) due to a transport motion (B) of the windings on the storage body (K).

[0001] The invention relates to a feeding device of the kind disclosedin the preamble part of claim 1.

[0002] A feeding device of this kind is known from DE 30 32 971 C. Thisknown feeding device is operated alternatingly together with at leastone further similar feeding device. The feeding device, in particular,is a so-called measuring feeding device apt to measure the length of theyarn inserted during a pick. For this purpose four radially oriented,pin-shaped stop elements provided in the storage body are coupled to aplanetary gear which is driven from the drive shaft of the windingelement and which displaces each stop element from a position close tothe winding element and radially distant from the storage surface to aposition in front of a just forming winding of the yarn exiting from thewinding element and then in axial direction into the stop position inwhich the withdrawn yarn is caught at the stop element. Subsequently,the stop element again is displaced in radial direction and away fromthe windings. The stop element functions as a conveying element for thewindings on the storage body and terminates the respective pick. Sincethe stop element is not able to start the pick, a controlled yarn clampis provided downstream which clamps the yarn while the stop element isdisplaced away from the windings. The opening movement of the yarn clampinto the passive position then starts the pick. As each stop elementmoves only relatively slowly with the power drive and as the power driveneeds a lot of space, the storage body has to have an undesirably largediameter (strong ballooning effect). To achieve a high pick frequency atleast one further, similar feeding device is needed which operates inalternation. The mechanical load for the yarn is high. The mechanicalload and the strong ballooning effect caused by the large diameter ofthe storage body tend to cause frequent yarn breakages or pick faultsand lead to insertion delays in case of high yarn withdrawal speed.

[0003] A similar feeding device is known from EP 0 250 359 A. Each stopelement is one tooth of a gear wheel. Each tooth gradually is pushedbetween the windings on the storage surface as a consequence of thedriving motion of the gear wheel derived from the driving shaft of thewinding element, and is then conveyed forwards together with thewindings before the tooth terminates the pick in the stop position. Theyarn clamp needed for starting the pick is provided at the storage body.Due to the slow movement of each stop element in the feeding device andbecause of the large mounting space of the drive in the feeding device,a storage body having a relatively large diameter is needed for elevatedpick speeds. The large diameter leads to an undesirably strongballooning effect (high mechanical load in the yarn and considerablepick flight time delays).

[0004] It is an object of the invention to provide a feeding device asmentioned in the introduction which can be used for high pickfrequencies and high pick speeds even in case of delicate yarn material,which operates substantially without disturbances and which allows toachieve optimally short insertion times.

[0005] Said object is achieved by the features of claim 1.

[0006] The combination of a small diameter storage body and a stopelement which axially is moved into the stop position exclusively by theadvancing motion of the windings allows surprisingly to employ the yarnfeeding device substantially without disturbances even in case of highpick frequencies and/or high pick speeds and even with delicate yarnmaterial. The small diameter storage body significantly reduces theballooning effect or the kinetic energy intermediately stored in a yarnballoon, respectively, such that very high insertion speeds and inparticular short insertion times can be achieved without excessivemechanical load for the yarn. The small diameter storage body, however,needs a large number of windings for each pick. Mechanical disturbancesof the movements of the windings on the storage body by the stop elementshould be avoided. This prerequisite is fulfilled when the stop elementis moved exclusively axially into the stop position by the windings. Thestop element does not need a drive for this movement, when the stopelement is taken along with the windings and follows the advancingmovements of the windings with minimum or even no mechanical resistance,which advancing movement of the windings is generated in a suitable wayby the winding process, (the stop element is dragged by the windings).Since the axial movement of the stop element into the stop position doesnot need any control from outside or from inside, the drive of the stopelement only has to control the precise engagement of the stop elementbetween the windings and to release disengagement again later insubstantially radial direction. In the combination these features resultin a synergy effect leading to high operational reliability even in caseof high yarn speed and/or to short pick times and/or high pickfrequencies. A small diameter storage body means a storage body whichhas a significantly smaller outer diameter in contradiction to theconventional tendency of feeding devices having a yarn length measuringfunction. In feeding devices having a yarn length measuring function,namely a large storage body is provided to have as few windings aspossible on the storage body for each pick and also to have onlyan-axial short yarn supply on the storage body.

[0007] A conventional controlled yarn clamp may under certain conditionsnot be good enough to cope with high pick speeds and to precisely startthe pick in adaptation to the weaving machine cycle. For this reason theyarn clamp is equipped with a quick opening mechanism to assist in thepositive effects of the small diameter storage body and of the stopelement which only is moved by the windings into the stop position. Theyarn clamp in this case is able to start the pick at a preciselypredetermined point in time and particularly rapidly, e.g. within only afew milliseconds or even in a shorter period of time.

[0008] Expediently, the small outer diameter of the storage body definesa curvature of the circumference of the storage surface which at leastsubstantially corresponds with the natural capability of natural,synthetic or compound yarn material to store a smallest unforcedcurvature. The yarn windings will lie relatively powerless, relaxed andin good order on the storage body. The rapid withdrawal of the yarn fromthis very small outer diameter storage body then only leads to a minimumballooning effect. The result of the natural capability of the yarn tostore a smallest unforced curvature means a certain bent yarn found whena free yarn section first is bent on a smooth surface to a very smallloop and is then released. This loop expands somewhat but maintains thena residual curvature. This residual curvature is used as a guideline fordimensioning the outer diameter of the storage body. Astonishingly, ithas been found that different yarn qualities and different yarnmaterials with very few exceptions develop very similar unforcedresidual curvatures and for that reason can be processed well on thesmall diameter storage body.

[0009] In case of an outer diameter between about 25 mm to 55 mm,preferably even in case of about only 35 mm to 40 mm, the ballooningeffect even in case of high pick speed is desirably weak. (Thecentrifugal force in the yarn is about proportional to the square of theradius of the curvature.) The small diameter allows astonishingly shortinsertion times even with moderate energy input, because the yarn isvery willing to be withdrawn easily. The small diameter storage body mayeven be expedient for feeding devices for projectile or rapier weavingmachines, e.g. in co-action with a withdrawal brake cooperating with thesmall diameter storage body. In such a case the stop element and theyarn clamp may be omitted.

[0010] The outer diameter may be so small that the axial length of thestorage surface is substantially larger than the outer diameter.

[0011] Expediently, the stop element is connected by a hinge with aradial adjustment drive provided axially stationarily. The radialadjustment drive adjusts the stop element precisely timed and reliablyinto engagement in front of the just arriving yarn winding exiting fromthe winding element. The hinge or the bending section, respectively,offers the necessary degree of freedom for the stop element thanks towhich the stop element will be brought into the stop position togetherwith the windings and substantially without any counter force only bythe advance movement of the windings on the storage body.

[0012] In order to axially return the stop element in front of the firstformed winding to prepare for the next yarn length measuring function anaxial adjustment drive is employed which returns the stop element whichmoves about the hinge or the bending section and after the stop elementfirst has been brought radially into the release position.Alternatively, even several sequentially operating stop elements may beemployed instead.

[0013] In the stop position the stop element is caught at an axial stop.This stop may be provided in the storage body or even radially outsideof the storage body.

[0014] Catching the yarn in the stop position of the stop element causesthe undesirable stretching effect or whiplash effect due to themomentary deceleration of the mass of the yarn. As a counter measure itis particularly expedient to associate an impact damper to the stopelement in the stop position for alleviating/moderating the stretchingeffect or the whiplash effect. That measure reduces the danger of a yarnbreakage considerably. The impact damper dissipates energy byresiliently giving way. The energy meant is introduced by thedecelerated yarn into the stop element. The stop for the stop elementmay move e.g. counter to spring force over a small travelling strokeeither in axial direction, in an inclined direction or incircumferential direction of the storage body, respectively, in order todissipate the energy. The stop element even may be elasticallydeformable in itself in order to carry out the impact damping effect assoon as the yarn is stopped abruptly when the stop element has reachedthe stop.

[0015] In order to precisely control and predetermine the point in timeof the start of the pick by the yarn clamp, it is expedient to open theyarn clamp by an actuating solenoid and to provide for the armature ofthe actuating solenoid a certain idle stroke in relation to the clampingelement of the yarn clamp. As soon as the actuating solenoid is excited,the armature uses the idle stroke to first accelerate free from the massof the clamping element and the oppositely directed spring force, andfirst to build up a lot of kinetic energy during the acceleration, andthen to displace the clamping element abruptly into the passive positionafter the idle stroke has been passed with high acceleration and/or highkinetic energy. In this way a yarn clamp opening time may be reachedwhich is in the range of only a few milliseconds or even shorter.

[0016] In view to a precise yarn control in the operational phase inwhich the stop element is brought from the stop position into therelease position, it may be expedient, to move the yarn clamp whichclamps the yarn substantially opposite to the withdrawal direction ofthe yarn towards the storage body. For this purpose a displacement driveis used, e.g. a stepper motor, which shifts or pivots the yarn clamp. Bymoving the yarn clamp while holding the yarn closer to the storage bodythe yarn section between the yarn clamp and the stop element placed inthe stop position will be relaxed such that no significant stretchingtension will be present in this yarn section when the stop elementfinally is displaced substantially radially out of the stop position.Such a yarn stretching tension, otherwise, would result in an abruptrelaxation during the movement of the stop element causing a disorder inthe yarn windings on the storage body. First, after the stop element hasbeen brought into the release position and/or after the yarn clamp hasbeen brought into the passive position, the yarn clamp again is returnedin the opposite direction.

[0017] Although the ballooning effect can be ignored in case of such asmall storage body, the yarn may carry out a rotating movement in thefinal phase of the pick and within a movement space in which it mightget caught by the yarn clamp or in the clamping section of the yarnclamp. For this reason the yarn clamp should be removable out of thismoving area.

[0018] An embodiment of the object of the invention will be explainedwith the help of the drawings. In the drawings is:

[0019]FIG. 1 a perspective view of main components of a feeding deviceaccording to the invention,

[0020]FIG. 2 a schematic side view of a yarn processing system employingthe yarn feeding device of FIG. 1, and

[0021]FIG. 3 a schematic longitudinal section of a detail.

[0022] A feeding device F (FIGS. 1 and 2) having a yarn length measuringfunction, for a weaving machine T, comprises a stationary carrier 1. Astorage body K is provided at the carrier 1. The storage body K may e.g.be similar to a rod cage having axially extending rods 3, the outersurfaces of which define a substantially cylindircal storage surface 4tapering in FIG. 1 towards the right end. The rods 3 are secured by footparts 5 to the carrier 1 such that they may be adjusted radially withina certain range (radial adjustment devices 6), in order to allow to varythe outer diameter D of the storage body and to adapt the winding lengthto the weaving width of the weaving machine. The outer diameter D of thestorage body K defines a circumferential curvature of the storagesurface 4 which circumferential curvature substantially corresponds tothe natural capability of natural, synthetic or compound yarn materialto store a smallest unforced curvature. The outer diameter D e.g.amounts only between about 25 mm and 55 mm. Preferably, the outerdiameter D is only about 35 mm to 40 mm. The axial length of the storagesurface 4 (L in FIG. 2) may be longer than the measure of the outerdiameter D.

[0023] A winding element W rotates around the outer circumference of thecarrier 1 (arrow 2), e.g. a winding tube which is connected to a notshown hollow drive shaft.

[0024] At the lower side of the carrier 1 two of the rods 3 are combinedto a rod 3′ forming axial stop 7 for a stop element S. A resilientlyyielding impact damper G (indicated in dotted lines) may be associatedto the stop 7. The stop element S could even be provided at anotherposition and not at the lower side.

[0025] A clamping section 8 of a yarn clamp C is provided in front ofthe free front end of the storage body K, substantially axially alignedto the position of the stop element S. The yarn clamp C includes,preferably, a quick opening mechanism 9 for moving a clamping element 13counter to the force of a spring 12 into a passive position (to open theyarn clamp) in which a yarn Y first held in the clamping section 8 isreleased. For example, an armature A of an actuating solenoid M isdriven in the direction of an arrow 14, to displace the clamping element13 from the clamping position shown in FIG. 1 into the passive position.

[0026] In addition, the yarn clamp C itself may be moved back and forthsubstantially parallel to the axis of the storage body or along an arc(double arrow 11, 11″), e.g. by pivoting the yarn clamp.

[0027] The schematic sectional view of FIG. 2 shows how the yarn exitingfrom the winding element W is wound in subsequent yarn windings YT onthe storage surface 4 of the storage body K, in order to form anintermediate yarn supply. The yarn Y is then withdrawn intermittently byan insertion device E of the weaving machine T out of this yarn supply.The weaving machine T e.g. is an airjet weaving machine.

[0028] In the shown embodiment the yarn windings on the storage body Kin FIG. 1 are conveyed forwards by a permanent winding process of thewinding element 2. They are conveyed forwards in the direction to thefront end of the storage body K (conveying motion B). Alternatively, inFIG. 2, in dotted lines, an advance assembly V is shown which e.g. isdriven by the drive shaft of the winding element W and which separatesthe yarn windings YT from each other and/or conveys them in thedirection towards the front end of the storage surface.

[0029] The stop element S is a pin 15 which is connected via a hinge ora bending section 16 with an axially stationary radial adjusting drive17 which, e.g., is a solenoid drive. The radial adjusting drive 17 isdesigned to move the hinge 16 in the direction of the double arrow 18back and forth, particularly in order to push the stop element S intoengagement between the windings YT (as shown) or to pull the stopelement S into a release position (not shown) in which the stop elementS does not have any influence on the windings YT. In full lines the stopelement S is shown just engaging into the path of the first producedwinding YT. During the further rotational movement of the windingelement W permanently new windings are formed. The conveying motion B ofthe yarn windings YT moves the stop element S into the stop position atthe stop 7 (shown in dotted lines). The pin 15 has a degree of freedomin the hinge or the bending section 16 thanks to which it may follow theconveying motion B substantially without counter force. At the end of apick the yarn Y abruptly is blocked against further withdrawal in thestop position of the stop element S. During the pick the yarn clamp Cremains in the passive position. The stop 7 may even be positionedoutside of the storage body K, as indicated at 7′, e.g.

[0030] After the end of the pick the yarn clamp C in its position shownin full lines in FIG. 2 is brought into the clamping position such thatthe yarn clamp C holds the yarn. Then the stop element S is displacedout of the engagement with the windings into the release position by theradial adjusting drive 17.

[0031] An axial drive 19, e.g. a solenoid, displaces the stop element Sin the release position again into the initial position in which thestop element S (shown in full lines) may be brought in engagement againin front of the first developing winding. As soon as a pick has to startdepending on the cycle of the weaving machine, the yarn clamp C isadjusted into the passive position. Thanks to the further rotationalmotion of the winding element W the stop element S again is brought bythe windings YT into the stop position in which it later terminates thepick.

[0032] The yarn section between the yarn clamp C and the stop element Sis held stretched out, when after the termination of the pick and afteradjusting the yarn clamp C into its clamping position the stop element Shas reached the stop position (the insertion device E normally builds upa basic tension force in the yarn). The stretching of this yarn sectionmay result in an abrupt relaxation of this yarn section when the stopelement is pulled back into the release position. The abrupt relaxationcould cause a disorder of the windings on the storage body (formation ofsnarls or tangles). As a counter measure here the yarn clamp C is movedby the drive 10 into the position 11′ in FIG. 2, to allow the stretchedyarn section to relax, and while the stop element S is in the stopposition and the yarn clamp C is adjusted into the clamping position,respectively. As soon as then the stop element S is brought into therelease position, or even after also the yarn clamp C has been adjustedinto the passive position, the yarn clamp C again is returned into theinitial position by the drive 10.

[0033] The yarn clamp C, e.g. may be moved completely out from themotion area of the yarn Y (pivoted position Q in FIG. 1). For thisfunction as separate actuator (not shown) may be provided, or even thedrive 10 may be used. Alternatively, a shielding could be moved over theclamping section 8. Or, at least, a deflector could be provided at theyarn clamp C to avoid the danger that the yarn might become caught.

[0034] The yarn clamp C in FIG. 3 has, analogous to FIG. 1, atube-shaped housing 20. A spring 12 presses the clamping element 13 inthe clamping section 8 against a clamping surface 21 (clampingposition). The quick opening mechanism 9 contains the solenoid M whichdisplaces an armature A in the direction of an arrow 14 upon excitementin order to actuate the clamping element 13 counter to the spring 12 toadjust the clamping element 13 from the shown clamping position into thepassive position and to release the yarn. An idle travel stroke 23 isprovided in the clamping position and with the solenoid M not excitedbetween the armature A and the clamping element 13. Upon excitement ofthe solenoid M the armature A uses the idle stroke 23 to accelerate asstrongly as possible and to build up kinetic energy, and to move theclamping element 13 with high force and as rapidly as possible firstafter having passed the idle stroke 23. In this fashion the opening timeof the yarn clamp C may be reduced only a few milliseconds or even less.

[0035] The armature A maintains the clamping element 13 in the passiveposition as long as the solenoid M is excited and until the stop elementreaches the stop position and terminates the pick. Then the solenoid isde-energised. The clamping element 13 now returns into the clampingposition under the force of the spring 12. The armature A is returnedinto its initial position by a separate, e.g. very weak, return spring22. In the initial position of the armature A again the idle stroke 23is adjusted with the predetermined magnitude.

1. Feeding device (F) having a yarn length measuring function for aweaving machine (T), comprising a winding element (W) driven forrotation; a stationary storage body (K) defining a storage surface (4)for intermediately storing a yarn supply consisting of windings (YT)conveyed on the storage body with a conveying motion (B) in withdrawaldirection, the yarn (Y) being intermittently withdrawn in picks from theyarn supply, at least one pin-shaped stop element (S) which is movablesubstantially axially and radially in a movement control assemblyarranged outside of the storage body (K) between a release position forreleasing the yarn (Y) and an engagement position for engaging at theyarn (Y), the stop element (S) in its engagement position being axiallymovable into a stop position terminating a respective pick, and acontrolled yarn clamp (C) provided downstream of the stop element (S)for starting a respective pick, characterised by the combination of thefollowing features: a) a small diameter storage body (K), and b) a stopelement (S) which in its engagement position is moved axially into thestop position exclusively by the windings (YT) and the conveying motion(B) of the windings (YT).
 2. Feeding device as in claim 1, characterisedin that the yarn clamp (C) is adjustable between a passive position anda clamping position, and that the yarn clamp (C) comprises a quickopening mechanism (9).
 3. Feeding device as in claim 1, characterised inthat the outer diameter (D) of the storage body (K) defines the storagesurface (4) with a circumferential curvature corresponding at leastsubstantially to the capability of natural or synthetic or compound yarnmaterial to store a smallest unforced curvature.
 4. Feeding device as inclaim 1, characterised in that the outer diameter (D) of the storagebody (K) amounts between about 25 mm and 55 mm, preferably amounts toabout 35 mm to 40 mm, respectively.
 5. Feeding device as in claim 1,characterised in that the axial length (L) of the storage surface (4) upto the position at which the stop element (S) in its stop positionco-operates in yarn blocking manner with the storage surface (4) islarger than the outer diameter (D) of the storage body (K).
 6. Feedingdevice as in claim 1, characterised in that the stop element (S) isconnected via a hinge or a bending section (16) to an axially stationaryradial adjusting drive (17), and that the stop element (S) comprises adegree of freedom in the hinge or the bending section (16) to carry outaxial movements relative to the radial adjusting drive (17) only by theconveying motion (B) of the windings (YT) in the yarn supply wound onbehind the stop element (S).
 7. Feeding device as in claim 1,characterised in that the stop element (S) in the release position issubstantially axially movable opposite to the conveying motion (B) ofthe windings (YT) by an axial adjusting drive (19), preferably by usingthe degree of freedom in the hinge or the bending section (16),respectively.
 8. Feeding device as in claim 5, characterised in that thestop element (S) in its stop position abuts an axial stop (7, 7′),provided either in the storage body (K) or radially outside of thestorage body (K).
 9. Feeding device as in claim 6, characterised in thatan energy dissipating impact damper (G) is provided, preferably in thestorage body (K), for the stop element (S) co-acting with the stopelement (S) when the stop element (S) reaches the stop position. 10.Feeding device as in claim 2, characterised in that an actuatingsolenoid (M) is provided in the quick opening mechanism (9) of the yarnclamp (C), that the yarn clamp (C) is maintained by spring force (12) inthe clamping position, that a clamping element (13) is movable counterto spring force (12) into the passive position of the yarn clamp (C) byan armature (A) of the actuating solenoid (M), and that an armatureacceleration idle stroke (23) is defined between the armature (A) andthe clamping element (13) when the actuating solenoid (M) isde-energised.
 11. Feeding device as in claim 2, characterised in thatthe yarn clamp (C) is movable back and forth at least substantiallyparallel to the withdrawal direction of the yarn (Y) from the storagebody (K) and in relation to the storage body (K), preferably by means ofa pivoting or a linear displacement drive (10), the displacement travelstroke (11) of which are adapted to the movement at least of the stopelement (S) such that the yarn clamp (C) is adjustable in the directiontowards the storage body (K) when the stop element (S) has reached thestop position and when the yarn clamp (C) is adjusted into the clampingposition, and is adjustable again in the opposite direction after thepassive position has been adjusted.
 12. Feeding device as in claim 2,characterised in that the yarn clamp (C) temporarily is removed out ofthe yarn moving range, preferably by means of a displacement drive (10).